A touch-panel interface accompanying a device typically displays a button area on a LCD (Liquid Crystal Display) and enables operations by the user's touching of the button area. A problem of this type of touch-panel user interface is that the user has a difficulty in identifying the location of a button since the “button” is a mere two-dimensional image displayed on the panel, rather than a physical button. Furthermore, lately along with multi-functionalization of the device and further complication of operation, a design and layout of the window/screen has become more crowded with data and multiple buttons. The foregoing factors contributes to the user's difficulty in operating such a device, where the user has trouble in intuitively finding the target operation buttons that are randomly or haphazardly arranged on the screen.